This application relates to and incorporates herein by reference Japanese Patent Application No. 2000-130811 filed on Apr. 28, 2000.
The present invention relates to a method and apparatus for measuring and adjusting resonance frequency of resonators.
In conventional filters having resonators, the resonance frequency of each resonator is adjusted by means of a dielectric material used in the filters or by trimming a conductive pattern of the resonator by a laser or the like. In the former adjustment, the effective permittivity is adjusted by a screw equipped with the dielectric material at the head thereof. In the latter adjustment, the conductive pattern is partlycut out by the laser.
In either case, the resonance frequency is adjusted while checking for the response of the filter provided on a measuring apparatus. It is therefore difficult to determined how much each resonator should be adjusted, particularly when the number of resonators increases and the number of locations of the required adjustment increases.
It is proposed to measure the resonance frequency of each resonator individually by the use of probes. However, if a plurality of resonators are provided on a single substrate, a resonator to be subjected to the resonance frequency measurement and other resonators interfere each other through electromagnetic coupling. Therefore, the probes do not ensure an accurate measurement of the resonance frequency of each of the resonators.
It is therefore an object of the present invention to provide a method and apparatus for measuring and adjusting resonance frequency of a plurality of resonators individually without being influenced by electromagnetic coupling between the resonators.
According to the present invention, a plurality of resonators are formed on a substrate. In measuring resonance frequency of the resonators, a conductive plate having an opening are placed above the substrate so that all the resonators other than one resonator which faces the opening are covered with the conductive plate. The resonance frequency of each resonator is measured in sequence while moving at least one of the conductive plate or the substrate.
Preferably, each resonator is made of a superconducting material and the resonance frequency is measured in a vacuum chamber. Each resonator is adjusted in shape by a laser trimming or providing a dielectric film in correspondence with the measured resonance frequency so that all the resonators have a fixed resonance frequency.